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MDD owner Feedback on CHUD Tools Nap modeReturn to News Page

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Dual G4 MDD owner Feedback on CHUD Tools Nap mode
(to lower CPU temperatures)

Posted: May 12th, 2004
Reports Last Updated: Sept. 26, 2009
(Revised 10/17/2016 to remove old/obsolete links.)

Notes on CHUD 4.x versions The latest CHUD Tools (v4.x non-beta) (available at Apple's developer FTP site (was ftp://ftp.apple.com/developer/Tool_Chest/Testing_-_Debugging/Performance_tools/) or you can use the CHUD Updater utility) no longer has the CPU "NAP" mode option anymore for users of some systems like the Mirror Drive Door (Dual CPU) models, although it does still appear for some other systems like the Powerbook G4. (Version 3.5.2 still had the NAP mode option for MDD owners - check Apple's FTP site for it.)
BTW - Older versions of CHUD had a "Hardware" preference panel instead of the "Processor" panel. (If you have CHUD already installed, use the CHUD remover utility before installing any other version.)

This page has MDD G4 tower owner reports on using CHUD's Nap mode (via the "Processor" system Prefs pane in CHUD 4.0x, the "Hardware" prefs pane in older verisons) to enable Nap mode for lower CPU temperatures. Note that Single G4 MDD towers have Nap enabled by default based on reports - dual G4 CPU models do not. Earlier CHUD versions (3.0.x) were reported here last December to have caused problems like freezes with those systems when NAP mode was enabled, however some users of v3.5.2 have said they used NAP mode on their MDD Dual G4 system OK (including some OS X 10.4/Tiger user). One of the earlier reports from a reader that saw problems noted disk corruption after a freeze/crash.) If you have CHUD already installed, use the CHUD remover utility before installing any updated version.
  Several MDD owners have replied to the request for feedback with reports on using Nap mode to reduce CPU temperatures. Remember NAP mode is off by default with the MDD G4 Dual CPU models and any restart/reboot will disable it again. A -single- CPU G4 MDD owner said he sees Nap mode still enabled after a reboot - but not on any Dual G4/MDD that I have seen.)

MDD Owner Reports on CHUD 3.5.x (most recent first)
Note: for those reporting problems with NAP mode enabled, I'm assuming that the system was stable normally. (NAP mode is off by default MDD Dual G4 models normally and after every restart it will be off again.

(added Sept. 26th, 2009)
"I have a PowerMac Dual 867 MDD which has been upgrade with the Sonnet 1.6Ghz MDX Duet CPU upgrade. I have 2 Optical drives and 4 hard drives installed. In addition I have an Adaptec 2930U, a SIIG II USB 2.0 card, and a Firewire 800 card installed in the PCI slots. My Video card is a flashed ATI 8500.

Though I never checked the CPU temperature before the Sonnet upgrade, after the upgrade I used Temperature Monitor to check the CPU and found that the CPU Board was reported as at 57-58 degrees C depending upon use (very stable regardless of CPU load) . Temperature Monitor reports that the maximum CPU Board temperature should be 62 degrees C (I have no idea whether that is true). (some upgrades have a -board- temperature sensor (G4 CPUs no longer do since the early 7400/7410 series IIRC (which even motorola noted was inaccurate, and abandoned it) although many macs have sensors adjacent to the CPU. The actual CPUs are typically rated for at least 65C internal junction temperature (many are higher rated - 85C or even 105C ratings in some cases.)

While running System 10.4.11 I installed CHUD 3.5.2 and checked the NAP option in Hardware preferences. The CPU Board temperature idling or under a light load dropped to about 42 degrees C. When under heavy load (such as compressing a movie using FastDVDCOPY), the temperature will rise to about 56 degrees C and then level off, dropping back to 42 degrees C after the operation is completed and the CPU load falls off. Placing Enable NAP in the applications folder and setting it as a startup item initiates NAP at startup.

It should be noted that when working in any classic application when booted into OSX or when booted into System 9 (as CHUD is OSX only) , the NAP option is defeated and the CPU Board temperature will rise to the levels seen without CHUD's NAP option checked. Upon going to a OX application from the classic application, the NAP feature takes hold again and the temperature drops even though classic is still running.

I also installed CHUD in OS 10.5.8 and the NAP option works fine though as noted by someone else the L2 cache size is reported incorrectly. However "About This Mac" still reports it correctly. More importantly, Enable NAP does not seem to be able to activate the NAP option in CHUD under OS 10.5.8 reporting an error. If anyone can suggest how Enable NAP can be made to work in 10.5.8 I would appreciate it.
(See earlier post below which was originally added to the MDD PS fan swap article but also includes notes on CHUD NAP/OS X Leopard script - forgot to add it here back in early July.)

(he later wrote)
I came across an AppleScript which is supposed to the job of Enable NAP even with 10.5. (from an OSXhints page, also linked in the previous report below w/CHUD script) I have modified it a bit (to avoid needing to give the AppleScript permission to run) and it works fine on my machine. Remember that the Access Devices button in Universal preferences must be checked for the script to run. The script reads,

tell application "System Preferences"
   set current pane to pane "Hardware"
   tell application "System Events"
      tell application process "System Preferences"
          set napModeBox to checkbox 1 of group 1 of window "Hardware"
           if value of napModeBox is 0 then
              click napModeBox
           end if
      end tell
   end tell
   close the first window
end tell

I am also attaching the script as an Application (Run Only). (EnableNAP1.zip, no longer available)

CHUD + MDD Fan Replacements Revisited (July 2009) (from an early July 09 update to the original article here on First Fan Mods in a PowerMac G4 MDD Tower)

(from early July 2009 - CHUD/10.5 comments farther down)
"I have a MDD G4 (Dual 1.25 FW 800 model, with very long GeForce Ti 4600 128MB video card, USB2 PCI card, 1 optical drive and 2 hard drives) that I am retiring and giving to a family member. It is running Leopard 10.5.7. I couldn't bear to give it to her with the original wind tunnel fans, so I set out to upgrade the fans as per Martin Kaufmann's article on your site (see linked article above)
The challenge was that all of the fans he used to replace the G4's fans (in original article from 2002 here) are discontinued and impossible to find now. After much scouring, I settled on the following models:
$9.99 - Scythe DFS123812-2000 120x120x38mm Case Fan - for the 120mm fan which blows across the CPU - 2000 RPM, 87.63 CFM air flow, 32.91 dBA noise level - as in Martin's article, this pushes less air than the original at its peak, but runs constantly rather than variably - there are a couple of 25mm fans at Newegg which have better specs, but this one must be 38mm to fit.

$3.99 x 2 - PCQUEEN IPC-606010 60x60x10mm Case Fan (item #35-168-003) - for the 2 fans inside the power supply - 3300 RPM, 26.5 CFM air flow, 30 dBA noise level (compared to 38 CFM, 47 dBA before) - original was 60x60x25, but these ones had the specs I needed and fit fine - every fan I found that could push over 30 CFM had noise specs in the 40's dBA, similar to the original fans (no point in switching), so I thought I would gamble on these.

I followed the article exactly, including cutting the unnecessary yellow wires on both fan types, and changing the connectors. The fan mod for all three fans cost $18, took about an hour, and I am happy to report that the sound level is less than half of what it used to be (sounds like about 35-40% what it was before at its quietest), and never ramps up to the full RPM wind tunnel that it did before.

I was a little concerned that the PCQUEEN fans did not have as high air flow as the original power supply fans, but after pushing at maximum CPU load for a full hour and copying with both internal hard drives, the highest I can push the CPU temperature is 60.9 degrees celsius (141.6 F), which is on the high side but within acceptable parameters (not higher than what I've seen with the original fans). I can not make the CPU hit 61 degrees, no matter what I do. The hard drive temperatures are virtually identical to before, even when busy for a long time.

I wish I had measured at full load before the upgrade. Unfortunately I only measured the temperature idling. One note is that I have always had a PCI slot cooling fan in the top slot.

Before fan upgrade, idle:

  • CPU - 56 degrees celsius (note this is an adjacent sensor, not actual internal CPU temp)
  • Hard drive near CPU - 41 degrees celsius
  • Hard drive under optical drive - 32 degrees celsius

After fan upgrade, under heavy load for 1 hour:

  • CPU - 60.9 degrees celsius (141.6 F)
  • Hard drive near CPU - 40 degrees celsius
  • Hard drive under optical drive - 33 degrees celsius

The CPU temperature only dropped to about 60 degrees when the load dropped, so I enabled "Nap" mode (see http://www.macosxhints.com/article.php?story=20071101231643321)
Idling, using nap mode:
CPU - 41.1 degrees celsius
Hard drive near CPU - 40 degrees celsius
Hard drive under optical drive - 33 degrees celsius
Dual G4 users have reported problems with nap mode unless the G4 is switched to Single CPU before napping. So... As indicated elsewhere on the Macosxhints site, I use this script to activate nap mode and switch to single CPU:

tell application "System Preferences"
  set current pane to pane "Hardware"
   tell application "System Events"
       if not UI elements enabled then
           display dialog "GUI Scripting is not enabled. Enable?"
           set UI elements enabled to true
       end if
       tell application process "System Preferences"
           set napModeBox to checkbox 1 of group 1 of window "Hardware"
           if value of napModeBox is 0 then
               click napModeBox
           end if
           click radio button "Single CPU" of radio group 1 of window "Hardware"
       end tell
   end tell
   close the first window
end tell

This must be re-run after every new boot. Note that as the original Macosxhints post indicates, though this older version of CHUD tools will work in Leopard, the values it reports for the cache size etc. are not accurate.

So... After all of this and $18 I have a much quieter Mac that runs cooler than before. My only wish is that I would have found a 60x60x25mm fan that pushed mid-30's or greater CFM with only mid-30's or lower dBA noise level. Also, I wouldn't have minded a 120x120x38mm fan that blew above 100 CFM with a mid-30's or lower dBA noise level. If you or anyone else know of better ones I'm all ears! Also, I should note that if someone had 2 optical drives and 4 hard drives (as compared to my 1 optical drive and 2 hard drives) this fan mod might not be adequate.
I hope this helps your readers...
(Updated comments added 7/9/2009)
I have an important update to that G4 fan mod note I gave you.
I noticed that the 120mm fan wasn't pushing as much air as I thought it should, and I realized it was because the 2-pin fan connector on the motherboard wasn't providing enough power. (3 pin connectors typically are for adjustable/variable speeds. But if it's a constant speed fan then maybe the 2 pin wiring was using only 5V vs 12V? (higher voltage = higher rpm fan speed typically)) I put the 3-pin connector back on and used a 3 to 4 pin Molex adapter adapter to connect it to the 4-pin hard drive power cables -- voila! Lots more air. So... Following the directions in the older article exactly may NOT work depending on the fan you get. Also, using a 3 to 4 pin adapter is much easier than modifying the connector from 3 to 2 pins as indicated in the article.

I also moved the hard drive that was next to the CPU to below the optical bay, because the other hard drive under the optical bay was running much cooler.
Now my updated temperatures WITHOUT nap mode are:

  • IDLE CPU: 51.4 C
  • BUSY CPU after 15 mins: levels at 53.2 C -- much more healthy
  • Hard drive temps: idle 30/32 C, busy 32/35 C

I should note that I also tried a 92mm 50CFM fan right on the CPU heat sink, but this interestingly produced slightly higher temperatures (CPU idle 52.5 C, busy 56.1 C, same hard drive temps). Because it didn't help, I removed it.

With these new results, I am much happier, and would remove my caveat about only having 2 hard drives and one optical drive. I think you could fully populate the drive bays and still be fine.
Cheers, Graham J"

(Added 7/21/2009)
"After reading about Nap Mode for MDD G4s I decided to give it a try and it has lowered the CPU temps by 30°F/ 17°C. My MDD is a dual 1.0 GHz running 10.5.7, I had previously replaced the PSU and case fans and am pleased with the noise reduction but not the temps - both CPU and GPU were running in the low 60°s C. Swapping the aluminum heatsink for a copper 1.42 GHz heatsink only got a 4-5°drop. Filling most of the drive bays with 2 optical drives and 3 hard drives was contributing to the heat, but the biggest single temperature increase occurred when I put in a (flashed) GeForce 7800 GS. The video card sits very close to the CPUs and their temps were generally within a degree or two of each other.
I've been running Nap Mode for about an hour now and Temperature Monitor reports CPU 41°C, GPU 57°C. I am using CHUD Tools 3.5.2 and have the Enable Nap script in my Login Items.
If I run into any problems with heavier use, restarts, startups, etc. I'll let you know but the initial results look great. Thanks for your continued support of older Macs!
-David C."

Thanks David.

(Added 7/20/2009)
"I have installed the scripts to use with C.H.U.D. 3.5.2 (from ftp://ftp.apple.com/developer/Tool_Chest/Testing_-_Debugging/Performance_tools/) on my MDD 1.4 dual processor Mac with OS 10.4.11. I have been using the script to enable NAP on startup for over two weeks now and I have not experienced any freezes or corruption so far.

My MDD has 4 hard drives (3 Seagate and 1 Maxtor), two optical drives, 2 gig ram, and an ATI Radeon 9600 Pro graphics card.

Back in 2003 I installed(2) Vantec 60 mm Thermoflow Fans between the CPU and the rear grille. I also had a PCI slot fan installed at one point but it didn't have a noticeable effect on the CPU temp. so I removed it. (I had someone else in the past say that didn't help and thought it actually was a negative regarding airflow in the case)

I am currently retired in Greece and I have no A.C. in my office.
With an ambient room temperature of 88°F, before using NAP I was seeing CPU temperatures of 139°F and the HD closest to the CPU running a degree or two cooler.
Since installing and activating NAP, using a single CPU, the temp is 117°F to 119°F and the hard drive 115° to 119°F.
Using both CPU's, 121F° The hard drive is 119°F.
All of the other hard drive run much cooler, the two on the other bus are 112°
The fans are also running slower and quieter.

I can see no discernible difference using a single CPU for most of my daily tasks of word processing, email or surfing the web. FMP 9 seems to work fine on a single CPU. I turn on both CPU's if I am using Photoshop or other apps that need more resources.

I haven't tried Sleep mode because I have always had a problem with it. After waking I would experience a freeze and have to force restart.
Thanks for providing such an informative web site and thanks to Ken for providing the scripts.

Thanks Nick (and thanks again to Ed for sending the scripts).

(Added 7/6/2009, from 7/4 email)
"I have attached scripts to use with C.H.U.D. 3.5.2 on the MDD dual processor Macs. (ProcessorControlsFolder.zip which contains Nap on.app, Nap off.app, Single proc.app, dual proc.app, enable nap.dmg) I have successfully used the Enable NAP script by putting it into my Login Items. It will run at startup. You can see it appear temporarily in the dock and after activating NAP it will quit. On occasion it will not quit, so you have to manually quit it, but this does not happen very frequently (although I doubt if it creates a problem if it continues to run). I found a temperature drop of about 30 degrees F when the second processor was turned off. And I found no subjective difference in response of the Mac, a Dual 1.25 MDD with 1.25GB RAM running 10.4.11. It seems quite flawless on that Mac. The unit also has an Iogear USB 2.0 PCI card installed which creates no problem unless a storage device is attached when sleep occurs. I have not tried this with Leopard.
It is my understanding that C.H.U.D. 3.5.2 does not work with Leopard (I think some have used it with Leopard, but as with anything, some may have problems.), and that 3.5.2 is the latest version that will work on the MDDs for this mod.

(added 5/30/2006)
"I've been using CHUD version 3.5.2 for about a month now for the Nap feature on my Dual 1.25 MDD G4. What a difference! My Mac sounded like a dust buster before the installation. You could hear it from the other end of the house. Now, thanks to Nap, my Mac is quiet for the first time since purchase. I'm running Tiger 10.4.3 and have had no instability in relation to Nap at all. Like others I've read about, Nap became disabled upon each restart. To solve this I simply created an Apple Script saved as an application and added it to my startup items. Works great!
(reader FYI - See post below this one for a reader's site with scripts for this.)

I do have a question though. How does Nap work? Are there any long term effects on my processors or hard drive? Any information is greatly appreciated. (Enabling NAP mode allows the CPUs to throttle down when not taxed, reducing temperature and power use. If your MDD doesn't show any problems with NAP mode enabled (some did, like freezes, hangs, etc.), then it should have no ill effects on the hardware as far as I know. Later versions of CHUD Tools doesn't support enabling NAP mode on these systems however unless Apple changed that recently in the latest 4.x update. Reportedly, the single CPU MDD models have NAP model enabled by default.)

Oh, by the way it didn't lower my cpu temps as much as others I've read. Mine went from around 60° C to 53.5° but I am so pleased that the noise has stopped!

Thanks for all the info you provide. Without finding your site through Google, I'd be deaf by now :-)
Cheers, Nicki"


Scripts to Enable NAP Mode at Boot a reader sent a link to a page with Scripts to enable NAP mode at boot (link removed as web page no longer online) as well as toggling single/dual CPU use.

10.4.3 Notes: Although one MDD owner initially reported problems after the 10.4.3 update with CHUD 3.5.2 Nap mode, he later said it seems ok now. 4 other MDD owners wrote they've seen no problems in 10.4.3 w/CHUD 3.5.2 NAP mode.

Using CHUD 3.5.2 with OS X Tiger: (so far several say it's reliable in Tiger where it wasn't in previous OS versions)

(added 7/12/2005)
"Salutations from the sunny island of Mauritius (a small tropical island in the Indian Ocean)!!

After reading reports from users who have successfully used CHUD 3.52 on MDDs running Tiger (10.4.1), I though it would be a good idea to try it myself.

In the past, my dual 1GHz MDD running Panther crashed with Nap Mode enabled within less than one hour, irrespective of CHUD tools versions installed.

The two front hard drive bays as well as the one at the rear are populated. I also have two optical drives installed. No PCI cards added. Using Temperature Monitor, the CPU temperature recorded is usually around 58-61 degrees Celcius, slightly fluctuating depending on CPU load. During winter (now), room temperature here is around 19-22 degrees. In summer, the room temperature jumps to around 27-30 degrees.

With CHUD Tools 3.52 installed and Nap Mode on, the temperature dropped to around 45-46 degrees Celcius on low load (10-20%). At around 80-100% CPU Usage, the maximum temperature recorded was around 59 degrees.

A screen cap of Temperature Monitor's sensor measurements:


So far after seven hours uptime, no application has crashed (crossed- fingers...) and Tiger is behaving nicely...No apparent performance hit. I had no problem putting the system to sleep. However, with Nap Mode on, the audio output noise level has jumped significantly. It is especially noticeable on screen refreshing (moving and minimizing windows, using ExposŽ and Dashboard). The infamous EMI/ RFI noise of the MDD was present before but at a much lower level. With Nap On, it seemed to have amplified! Fortunately the iMic saves the day!

Thanks to you and all the Macheads who contribute to making Xlr8yourmac the most invaluable information source!
Regards, David V. "

(added 7/12/2005)
" Like many others, I had tried CHUD tools up to rev. 4 which cut off the "nap" feature in the Hardware panel. After reading the recent success story with CHUD Tools 3.5.2 and Tiger (10.4.1) I decided to try again with what appears to be better luck.

Machine specs are a MDD 1.4 Ghz Dual with the only extra internal hardware being a ATI Radeon 9800 Pro. Tiger 10.4.1 with CHUD Tools vers. 3.5.2.

I've been running most of the time with "nap" enabled and so far have not seen any misbehavior or outright lock-ups or crashes. They happened frequently when trying with Panther. Right now as I'm typing along with nothing much other running except Safari and Mail, Temperature Monitor is reporting 104 F at the CPU Board (79 F ambient temp).

The before "nap" temps were 137 F when initially testing went down fairly quickly to about 107 F.

Power Consumption: (extra data just FYI)
The machine draws 4.5 watts even when shut-down with power cord connected.
182 watts after startup and stabilized with processors idling.
114 watts after "nap" mode enabled.

All looks good so far (fingers crossed) and the Mac is using less power, dumping less heat into the room (not so bad in winter, bummer in summer), and the power supply is happier too I'd imagine...
-Michael D. "

(added 7/12/2005)
"I'm writing this now because I know if CHUD (v3.5.2) Napping causes my MDD dual 1.25 to freeze up, it will happen as soon as I write saying that it seems to be working under Tiger!!

The same version of CHUD caused freezes under OS 10.3 but perhaps, perhaps it will react differently under 10.4. It drops the CPU temperature by about 10-15C as measured by Temperature Monitor. I notice, though, that the computer does not go to sleep naturally under any settings I've tried in Energy Saver but will sleep if induced manually and seems to awaken quickly and normally.

Fingers crossed but OK for two days now.
-Gary "

(added 7/6/2005)
"I am using CHUD Version 3.5.2 on my Dual 1GHz, 133 bus speed (not 167, it was originally a single FW800 but I bought a new Apple Factory dual 1GHz processor/heatsink and had it installed at an Apple Dealer), 2MB level 3 cache per processor, 1.8 gig RAM, GeForce Ti 4600 128MB video card, Mirrored Drive Doors PowerMac G4.
This computer was so loud and hot that I was ready to sell it until I found this. Now, when using this version of CHUD, I enable the NAP setting and the temp. went from around 140 to around 109 !!!!!!!
At this very moment the machine is quiet and running at 109.3 degrees F. A 30 degree temp. drop and the computer is quiet! Also, all the application crashes I was having all the time have stopped.
I have been using this now for several months without problem. It feels like I have a new computer. I specifically downloaded 3.5.2 because I read that the later versions don't have this NAP feature. (CHUD v4.x doesn't have NAP mode option for MDD users) I understand that each machine is different, but this has saved mine as well as my sanity!
-Justin L.
(What OS version are you using)
I am using 10.4.1 currently, however I was on 10.3.9 at the time I initially started using this tool. I have had zero problems and it truly has saved my sanity. I was seriously ready to sell it! Right at this moment I am running at 108.7 degrees F, and that is with 2 hard drives, 2 optical drives, and an upgraded Titanium 128MB video card. Prior to using NAP, I never saw the temp. drop below 135. It is just amazing. I really feel for the others who are having the problem I was having with their MDD's, and I am real sorry that this doesn't work for everyone. It seems odd to me that it could vary so much from one machine to another when the machines are so similar. (Initial problem reports were from CHUD 3.0.x/OS X 10.2.x and there's an almost infinite number of variations in installed software/addons, plus the possible issue of G4 CPU chip revisions/steppings, etc.)
Anyway, thanks for your site, it is a fantastic resource. I personally own 6 Mac's - I am a bit obsessed - and I depend on site's like yours on a constant basis to keep them all in perfect shape. Thankfully they're Apple's, if they were PC's I could never manage to keep up with all the problems they would have !!!! I have one PC - a dell - and it is more trouble than all of my Mac's combined!"

(from 6/17/2005 news page post)" About a year ago I used CHUD 3.5.2 on my Dual G4 MDD 1.25. It was under Panther and I remember having some problems with the GUI locking up from time to time. (see other reports from MDD Dual G4 owners on the page linked below, NAP mode (to reduce CPU temps) problems were pretty common on Dual CPU models.) Then Apple updated CHUD and they stopped allowing the G4 chip to "NAP". I just forgot about it and installed a upper slot cooler to bring my CPU temps down. It worked good and I have been averaging about 127-131 degrees F with an ambient temp of 73 degrees F.

Reading a user forum the other day I read that a Tiger user installed CHUD 3.5.2 and seemed to have a very quiet Quicksilver G4. I figured what the heck and downloaded it and tried it again. It may be too early to tell but three day's now and no problems. (remember NAP mode gets reset after a restart/reboot.) I would usually have a lockup in about 24hrs. under Panther.
I noticed no noise reduction (was not loud before only when the temps exceeded 135 F) but my CPU temps have gone down to about 98 degrees F at an ambient temp of 73 F. (I doubt 98F is really accurate but then G4 CPUs don't usually report accurate temperatures as has been noted for years (also mentioned in Motorola's G4 spec docs since the 7400 models). However enabling NAP mode does reduce CPU temperatures.) As I write this my ambient temp is 67 degrees F and my CPU temp is 87 degrees F. Not bad at all. It really makes a big difference in the CPU temp overall.

I think (hope) that a change in Tiger allows this feature to work. No hit in performance. Everything seems snappy. In fact I think that the lower temps allows it to run better than before. I have burned CD's, used Photoshop, Surfed with Safari, used Mail and no problems to speak of so far.
Possible the readers here would like to hear this and try it again. I do believe that this 3.5.2 was the last version Apple released that allowed "NAP".
Thanks, Jerry "

(added 5/20/2004)
I just purchased a (single CPU) MDD 1.25 from Apple a month ago. I installed a temperature monitor (software based) right after I got it and have always had CPU temperatures around 93-97 degrees F. I noticed that the fans varied in speed based on CPU load and thought that was a bit awkward. Then I started looking at these CHUD reports about nap mode I decided to try it myself. I installed 3.5.1 and when I opened the preference pane nap was checked already! (it seems unlike the Dual CPU MDD models, NAP is enabled by default on the Single CPU models)
I unchecked it and the fan speed slowed down and the CPU temperature went up continually until it leveled off at about 112F! Go figure, nap was enabled by default on this system out of the box! The G4noise forums have also made mention that 10.3.3 enables nap by default on the systems that support it. I have to also note that other than a flakey stick of memory, my system has been perfectly stable since I plugged it in.
Love the site!!

Thanks Matt. Like the G5 Towers, the single CPU MDD towers must have NAP mode enabled by default based on reports. (No reason to install CHUD on a single CPU MDD model, unless for some reason you'd want to disable it.)

(added 5/20/2004)
I too have had the weird "auto-check" of nap-mode occuring on my G4 Single 1.25. (that's normal based on reports on -single- CPU MDD models as well as some other macs like the G5 towers.) Every time I turn the thing back on, I have to go in and uncheck nap mode. I've had to add the hardware pref icon to my menu bar so I could get to it quicker. Very annoying.
This also is occuring on my 800mhz G3 iBook! (it will appear checked/enabled on systems where Apple has that feature enabled by default. Disabling it will make the system run hotter typically)
How can I remove chud tools altogether? It's not worth the annoyance. I've had weird app crashes occurring lately on my G4 and am wondering if this is the culprit or if it's the QuickTime update.
Peace, Todd "

I'd leave NAP mode enabled (default) then if you're seeing problems with it disbled. The CHUD package has a remove CHUD utility.

(added 5/19/2004)
I have a Dual 1GHz MDD, 768 Megs ram, OS X 10.3.3, an extra 40 gig internal HD, an M-Audio Delta-66 card, Buffalo .11g wireless card, cable modem, and an added, faster CD-RW to supplement the Superdrive. Even after the fan/power supply replacement program my fan noise is pretty high since I've moved south. CHUD and Nap mode seemed like the answer. I was getting all the usual crashes everyone else has reported but I wasn't going to give up. I _really_ appreciate the quieter machine.

Long story short, I did everything I could to try to find out if there was anything consistent that caused the crashes and do whatever I could to make it stop crashing. After long processes and experimentation I have found that my machine stays stable after I do several things, all before re-enabling Nap mode--repair permissions, rebuild prebindings, run all the maintenance scripts, use Cache Cleaner to deep purge all my caches, and then restart at least one more time. Also running it with Nap mode disabled for a while seems to help stability.

Only after I install new apps or updates are there problems with crashing again. I then go through my ritual and offer my time as a sacrifice to the "gods" and things seem to stabilize again. Only one or two of these things may be necessary, but I got to the point where I do them all just to be sure. The most common activities seem to involve internet applications like Safari, Mail and sometimes iTunes, and as others have said waking from sleep. I assume what it boils down to is that Nap mode on a G4 has little or no tolerance of system issues.

I always have to re-enable Nap mode. Crashes not withstanding, I always leave my Mac on and it is rock solid stable without Nap mode. Without Nap mode on, temps typically run around 140 degrees. With Nap mode temps run around 100 degrees +/- 5. When working steadily in Classic or cpu intensive apps like Deck or Peak, or Final Cut temps rise back up. I notice fan noise decreases around 130 degrees. I would accept it if there were some way to keep normal operating temps around that if it meant a quieter _and_ stable machine.
Joseph F "

In limited use I've seen no freezes to date with CHUD 3.5.1 on a Dual 1.25GHz MDD w/10.3.3. After the earlier reports from some MMD owners of freezes when shutting down, sleep/waking from sleep, coming out of the screensaver, etc. I set Energy Saver settings to allow sleep (never do usually) and the screensaver and haven't seen a problem yet. (Letting the system go to sleep/waking it - forced sleep/wake, coming out of the screensaver and letting apps run for several hours. I can't say it won't have a problem in the future though (my main work machine is a Powerbook, so I don't use the MDD a lot.) If I saw any freezes with NAP mode enabled, I'd not use it period. (RAM has also been suspected as a factor in freezes, but assuming the systems were rock stable w/o NAP mode enabled.)

An updated report from Chris (his prev. comments are below dated 5/17/2004)

(added 5/19/2004)
My mac is in fact a dual 1.25 MDD (FW800)--sorry for the confusion.
One other thing I wanted to point out and perhaps get some feedback from other MDD owners on: I have only heard my MDD go into "wind tunnel" mode twice ever, and both occurrences where when the machine was very new (first month or so). I was one of the very first MDD FW800 owners (got the first machine available from our academic Apple reseller), and I believe it came with OS X 10.2.3 or 10.2.4.
I'm wondering if Apple has toned-down the fan parameters. I have seen my MDD get up to 148F before on a particularly long computational run. It sure seems like the "wind tunnel" mode should have kicked in-- this is way hotter than most PCs I have been around.
Personally, my MDD works great for me--wonderfully stable and fast enough for what I need--so I would like to keep it a few years, and I would rather that the fan would kick in and have to deal with the noise than have a melted-down CPU/Motherboard.

I have been experimenting with modifying the fan parameters in the AppleFan.kext that controls the fan, but I've seen really no differences by adjusting the threshold. If anyone has a 10.2.3 installation handy, I wonder if I could get their AppleFan.kext. Otherwise, when I get an opportunity I will try to pop in a spare hard drive and do an install of the OS that came with my machine.

I'm really not comfortable with my machine running at these temperatures in the long term. With software controllable fans it seems like we should be able to do better than this.
-Chris "

Apple also updated the firmware of earlier MDD systems (which also affected fan control as I remember).

(added 5/17/2004)
"I have been using CHUD on and off on my (Dual?) MDD 1.25 (FW800) machine, for several months (now CHUD 3.5.1). I've never had any stability problems whatsoever with stability of the machine. This machine runs 24/7 but I have another problem: with nap off (factory setting) the fan actually runs nice and quiet but very hot (approx 138F using ThermographX). I know I am probably in the minority, but I really feel my MDD 1.25 in with nap off is very quiet (my Athlon 1.0ghz by comparison is MUCH MUCH louder, but luckily I turn it on about once every other week).

When I turn on nap, I get *substantial* temperature improvement (approx 112F). However, the fan makes VERY annoying noises as it changes speed due to use. It is very irritating.
So unfortunately it seems I have to choose between running hot and quiet or cool and annoying. Has anyone else noticed a change (for the worse) in noise? (I had previously mentioned that with a Dual 1.25GHz MDD here (FW400/OS 9 bootable model), I noticed immediate an increase in fan speed/noise.) I am considering trying to figure out which fan it is that is so annoying (I assume it's the fan that blows over the heatsink) and see if I can replace it and see if the noise goes away.
It seems it would be a lot better for my machine if it ran cooler but it's really hard to sit in front of with nap on.
Thanks, Chris "

(added 5/17/2004)
"My dual 1.25 GHz MDD (dual boot) has been rock solid. I updated to CHUD 3.5.1 and tried NAP mode. While it greatly reduces the temperature, the system periodically locks up. The system, including the cursor, just freezes. The first time was on a sleep. The next time was a couple of days later in normal use. Without NAP mode, I never have it freeze like that.
The NAP setting is not retained over a reboot.
Wes "

(added 5/17/2004 - for some reason this 5/13 dated mail arrived days late.)
"I have MDD 1.25-SP and have used CHUD since I got this G4 in February ('04), one of the Apple Specials for $1099. Never had a problem, and have Nap enabled.
Gregory "

An update from a reader that previously reported freezes (I asked about his RAM, if the system was stable w/o Nap mode enabled, if he checked the settings after a reboot, any USB drivers/devices, etc.)

(added 5/13/2004)
"I've got 1 gig of ram ( purchased another 512meg module from Apple after purchase of machine last spring).

I do have a couple two or three 3rd party usb devices installed thru a Belkin 7 port hub (Powermate, Keyspan twin serial adapter, adaptec scsi adapter). I'll try disconnecting everything but the keyboard and Apple mouse to see if that makes a change. (some 3rd USB drivers may also poll the USB bus even if the device isn't connected - may or may not be a factor in problems though, but just a FYI.)

System stability is pretty good with out the nap mode enabled. I did have on direct tie in with system crash and nap mode because it crashed soon as I clicked on the nap mode button....
I'll give you feedback on the "baseline" usb testing.
Mike D.
(in reply to the question of Nap mode setting was retained/enabled after a restart)
No the nap mode for me has to be re-selected after reboot. "

That's what I've seen from two MDD Dual G4s which is why I was surprised that a Single CPU MDD owner (below - Thomas P.) said it retained the enabled setting after a reboot.

(added 5/13/2004)
"I installed CHUD a few months ago (earlier versions, then 3.5 and 3.5.1), and I think the Nap checkbox was checked by default (either that, or I don't remember having checked it...). Anyways, I never had a problem with this. MDD Single CPU G4/1.25 (at 1.58), switched on day and night. I don't care about the nap feature since there's Folding at Home almost always running and preventing any nap, but since it makes no harm I left it activated.
(since NAP mode is not the default (not checked) on any Dual G4 MDD I have ever seen (and tested 3.5.1 again today on a dual 1.25GHz) - I asked for verification)
I just tested. Uncheck Nap box, quit System Pref, reopen and verify Nap box is still cleared. Restart, then open Prefs -> the Nap box is checked! I tried a second time, same result. It sticks in the Nap enabled position, the opposite of your experience. (and other Dual G4 MDD owners as noted here)
Thomas P. "

This morning (5/13) I installed CHUD 3.5.1 on a stable/reliable Dual 1.25GHz MDD mac in 10.3.3 (no 3rd party devices or drivers added - not even a USB printer) and I had to check (enable) Nap mode in the Hardware system prefs pane (and a restart shows it unchecked as expected). In -very- limited testing this morning I didn't see any problem in shutting down or waking the system after sleep or from the sceensaver. (I normally set the system to never sleep but as a test I set the ES to sleep after 15min of inactivity to see if any problems were seen). So far OK, but again this is from very very little use. (I use a PowerBook as my work/mail machine and therefore don't get to use the MDD very much.)

(added 5/13/2004)
"Hi, just checked the newest version of the CHUD Tools. In the first turn I could run the MAC for 2 hours, than at shutting down it freezes. Second turn was just 5 minutes.
Now I've also compared the Power that the Mac is using. I've a Dual G4 1.25 Ghz with a PC to MAC modded GeForceFX5200 Ultra.
Without NAP, the MAC uses 111-113 Watt in idle. With Nap enabled, 69-72 Watt. That is a pretty good improvement. So, hopefully someday it will work without freezes on MACs.
Kind regards, Jan Z.
(he later wrote)
Maybe it has to do something with the power the mac is using. Everytime when it is less than 67 Watt, Mac does freeze. If I listen to Music or have just a Temperature monitoring Program running, that MAC will run endlessly long. (most that saw freezes indicated it was during some transition - if the CPU is being taxed it should not go into Nap mode.) But if he is doing nothing, he will freeze. So, just using Safari or something like this, don't use enough power. But with Music or the Temp Monitor MAC does run. Thats also why the MAC does freeze on standby or shuting down. Maybe I will try an other Powersupply with an adapter and look what will happen.
Interesting Problem, right? "

In -very- limited tests (idle mostly) a Dual 1.25GHz here hasn't frozen yet (let it go to sleep after 15min, it woke fine, woke from screensaver, etc. - but it's too early to tell if I'll see any problems with NAP mode enabled.) I also asked Jan about his ram, any addon devices/drivers, etc.

(added 5/13/2004)
"I am using and have for months used Chud 3.5 on a MDD dp 867. I also used the previous version of CHUD. I have never had any problems of any kind on this computer while using CHUD. I also support a 2gig G5 that does not have any stability problems.
People having the problems described at your site may also want to test RAM and USB devices.
Roger "

RAM or other addons are always a possible source of problems (even w/o NAP mode enabled of course) - but I assume those that saw problems with their system/config with NAP mode enabled didn't have those problems until they enabled it. (with so many possible system/hardware/driver/OS setting, etc. configurations, it's hard to troubleshoot what the problem is, but if freezes only happen with NAP mode enabled, then I'd avoid using it.) Apple noted CHUD 3.5.0 had a system folder permissions problem (incorrect owner/permissions) so anyone running 3.5.0 should probably remove it (with the utility) and update to 3.5.1 (if you wish to continue to use it.)

(added 5/13/2004)
"I am using a MMD dual 867 with PC2700 memory MacOS 10.3.3. temperature used to run above 130F all the time with fan belching and squeeking. When I first used CHUD (2.5???) in NAP mode the typical temperature dropped to around 92F. I then began noticing freezes at high CPU usage times; screensaver, several programs active at once, etc. Then, while trouble shooting the problem I noticed a problem with a couple memory sticks. I now use just 2X512Mb and have no problem at all. I reinstall one or two more memory, the problems return. I am waiting for my new memory to arrive and enjoying no freezes for days and days at a time.
(I asked if he had tested the removed dimms in the system only and if the system was stable w/o NAP mode enabled since if the ram was bad, it should also cause problems w/o NAP mode enabled.)
Yes, I tries each of 4 512Mb sticks one at a time. Also I tried various slot positions. I must have had the ram problem beore I ran CHUD. It just didn't reveal itself.
I have to re-enable Nap mode after each restart. If I just logout, and without restarting, the Nap mode stays enabled.
Jim T. "

" I have been trying every version of CHUD that comes out with my Dual 1Ghz MDD (1.25GB RAM). Every version causes freezes with "Nap" mode on. This latest version still freezes. The other thing I noticed about this latest version, was the CPUs would make a very high pitched squealing noise when I was doing something like say, dragging a window. In fact, the Marine Aquarium Screensaver would make the CPUs squeal really loud. Very interesting.
Jason K. "

The squeal I suspect is coming from the Power Supply (the same thing happens with the G5's when Nap mode is enabled (it is by default on the G5) as mentioned here last year in the article on G5 power supply squealing/chirping noises. The easiest way I can repeat this on the G5 is going from idle to selecting a startup disk in the control panel as it's searching for existing startup volumes, although other operations can also cause it. Disabling Nap mode usually solves that. But the CHUD Hardware settings don't 'stick' after a reboot and Apple does not recommend disabling Nap mode on the G5 as mentioned in that article.)

" I installed CHUD yesterday (11 May) on my MDD 1.25 DP (FW800) running 10.3.3. This was a fresh version of CHUD, no update. I got random lockups every hour or so, but the longest I had was just over two hours before completely freezing. Most lockups occur if the screen saver kicks in and you move the mouse to get back to the desktop, or trying to shutdown or put to sleep.
This version for me seems to be the most unstable compared to older revisions where I had lockups every two days or so. Generally the fan noise is much better and temperatures cooler, but I'm disappointed in the constant freezes.
Jason H. "

" Have a 1.4ghz dual G4 with 10.3.3 and have been trying CHUD tools with every iteration to reduce internal temps. The upside is that the CHUD software seems to be improving but I will still have occasional random crashes, and these seem to be happening under light or idle cpu loading.

From an engineering perspective the first question to ask is is the 7455 processor fully capable of "nap" mode with the proper software implementation? If it is (and does anyone know this specifically?), then its only a matter of working the bugs out of the software. I'll keep testing as new versions come out.
(when the first problem reports rolled in back in Dec., I wondered the same thing - were the problems due to bugs the software/OS, or does the 7455 really support NAP mode as implimented by CHUD. Or do some revs of the chip have errata that is a factor in the problems. And the almost infinite number of possible system software/hardware configurations (3rd party software/drivers, hardware, settings, etc.) could also be a factor perhaps. Some macs like the portables (and the G5) support bus slewing (reduced speeds/energy saving modes) and have options in the Energy Saver to set CPU performance (auto, highest, reduced) but not any MDD system I have seen. )

I've never seen it posted but I've taken actual input wattage measurements using a digital wattmeter to measure the actual input power changes with the turning on of "nap" mode and it is substantial, going from aprox. 145-150 watts at "idle" to approx. 80-90 watts with the "nap" mode enabled.

Temperature decreases are typically down from 132 deg. F. to around 102 deg. F as I'm typing this while in "Nap" mode.
Michael D "

" I've been using Apple's CHUD 3.5 primarily for the Nap feature to control (lower) temperature on my G4 MDD dual 1Ghz Powermac. Generally works for a day or two before I get a system freeze or other annoyance. I*m certain it*s related to switching this feature on. I still use it to lower the fan nois - I got a free replacement power unit from Apple but just haven*t found the time to swap out the noisy one which came with the computer. Would be interested to hear feedback from those who have updated to CHUD 3.5.1 to see if the stability problem has been addressed.
-- Glenn"

" I use Nap Mode on my Dual 867 every day. The main thing I've noticed with doing this is it freezes upon shutdown a lot of the time. I use it anyway because it cuts down on the heat inside the computer a lot so the fans don't go on louder. I did the power supply exchange program and it was great for a few weeks but it got louder again.
(I also did the MDD fan/PS swap last year - at first I noticed a big difference - but later it still seems louder than past G4 towers. But not the horribly annoying frequency the PS fans had before. And after the swap there's this almost clicking sound heard from the fans. I checked for anything hitting the fan blade and nothing seems to be, but it still sounds like it.)

(I asked if he was using 3.5.0 previously)
Yes I was using CHUD 3.5.0 before today. I do have 10.3.3 installed on my computer. The crashing problem at shutdown has been there since 3.5.0 was released for me. With prior versions it was more unstable than this with sometimes random freezes. The weird thing is that it's not consistent during shutdown freeze. I think it does it more if I leave my computer doing nothing for a while then shutting it down as opposed to work then shutdown. After the power supply exchange program installed I used to be able to hear the hard drive but that is no longer true with the fans always at a low hum and if NAP mode isn't enabled the fan is clearly louder so it's worth it to leave it on. With 3.5.1 I haven't had any random freezes and I've been running it since it was released. I did notice some permissions had to be repaired after installing it though. I tried a test shutdown and it worked fine but it didn't always freeze with 3.5.0 either. I will let you know if it does it.
(later in the day he wrote)
Just wanted to let you know that my computer has had two freezes while my computer was in an idle state with nap mode enabled and a crash during shutdown again. Apparently the problem hasn't been fixed."

" I've been using (CHUD) 3.5 since it came out on a DP867 (MDD) with 1.25 gigs of RAM. No problems at all, but the NAP mode does not keep the machine quite as cool as did older, buggier versions. Still, I get a temp reduction of 7-10 Celsius degrees (it was at least 15 degrees with the older CHUD tools).
Jeremy "

For G5 owners, CHUD Tools Hardware preferences pane was a popular way to stop the G5 power supply squealing/chirping noises by disabling "Nap" mode. (Although Apple reportedly does not recommend doing that.)

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